Transducers



April 7, 1970 .1. M. LAZAR 3,504,689

TRANSDUCERS Filed Aug. 30, 1967 2 Sheets-Sheet l INVENTOR. JEFFREY M. LAZAR ATTORNEY April 7, 1970 J. M. LAZAR 3,504,689

' TRANSDUCERS Filed Aug. 30, 196'? 2 Sheets-Sheet 2 FIG. 2

INVENTOR. JEFFREY M. LAZAR BY MIW ATTORNEY United States Patent 3,504,689 TRANSDUCERS Jeffrey M. Lazar, South St. Paul, Minn., assignor to Honeywell, Inc., Minneapolis, Minn., a corporation of Delaware Filed Aug. 30, 1967, Ser. No. 664,487 Int. Cl. F15c 3/02; F16k 11/07 U.S. Cl. 137-815 8 Claims ABSTRACT OF THE DISCLOSURE Apparatus comprising a chamber having a slideable piston therein for differentially varying the amounts of fluid vented from portions of the chamber on opposite sides of the piston, thereby producing a fluidic output signal.

The invention herein described was made in the course of or under a contract, or subcontract thereunder, with the Department of the Air Force.

BACKGROUND OF THE INVENTION SUMMARY OF THE INVENTION Briefly, the present invention comprises a piston moveable within a cylindrical cavity having an elongated fluid exhaust aperture, means for supplying fluid to the chamber on opposite sides of the piston, and a pair fluid outlet ports also on opposite sides of the piston. Displacing the piston within the chamber produces a diflerential fluidic output signal which varies in proportion to the mechanical displacement.

BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 discloses a position transduced, partially in section, having a fluidic amplifier connected thereto; and

FIGURE 2 discloses an alternate embodiment of the position transducer partially in section.

DESCRIPTION OF THE PREFERRED EMBODIMENT In FIGURE 1, reference numeral 10 designates a fluidic position transducer. The fluidic position transducer is comprised of a housing 11 enclosing a cylindrical cavity having an elongated fluid exhaust aperture 12, land a piston 13 longitudinally displaceable in the housing and having a first seal 14 and a second seal 14a. The fluid exhaust aperture 12 extends along the entire length of housing 11 but is partially hidden by a rod 16 which connects to piston 13 and extends through one end of the housing for connection to suitable mechanical or human drive means. The external end of rod 16 is shown connected to a handle to facilitate movement thereof. To the left of piston 13 is a first chamber 18 and to the right of piston 13 is a second chamber 19. A power source 20 supplies fluid to chamber 18 through a passage 22, a restriction 23, and a first inlet 21. Similarly, power supply 20 supplies fluid to chamber 19 through a passage 25, a restriction 26 and a second inlet 24. At the end of chamber 18 is a fluid outlet passage 30, and similarly, at the end of chamber 19 is a fluid outlet passage 31.

3,504,689 Patented Apr. 7, 1970 "ice A proportional fluidic amplifier is identified by reference numeral 33. Fluidic amplifier 33 has a power nozzle 34, a first control port 35, a second control port 36, a first outlet 37, and a second outlet 38. The first control port 35 connects to the fluid outlet passage 30, and the second control port 36 connects to the fluid outlet passage 31.

A scale 40 is shown attached to housing 11. An indicator 41 movable with rod 16 coacts with scale 40. By varying the position of indicator 41 and measuring the differential fluidic output signal between fluid outlet passage 30 and fluid outlet passage 31, the position transducer can be calibrated. Scale 40 may be graduated in units of differential pressure so an operator can then visually determine the magnitude and sense of differential fluidic output signal by observing the position of indicator 41.

In FIGURE 2, reference numeral 50 designates an alternate embodiment of my position transducer that has been found useful for converting rapid piston displacement into a differential fluidic output signal. Position transducer 50 comprises a housing 51 enclosing a cylindrical cavity having an elongated fluid exhaust aperture 52. Housing 51 encloses a first chamber 53 and a second chamber 54. A piston 55 forms one end of the chamber 53, and a piston 56 forms the other end of the chamber 53. A piston 57 forms one end of the chamber 54 and the piston 56 forms the other end of the chamber 54. The pistons 55, 56, and 57 are affixed to a rod 60. On each of the pistons 55, 56, and 57 there are seals to prevent fluid leakage past the pistons.

Aperture 52 does not extend the entire length of the housing as does fluid exhaust aperture 12. In operating condition pistons 55 and 57 are spaced from the ends of the exhaust aperture 52 and do not close off the aperture. Thus, displacing piston 56 varies the length of aperture 52 in communication with chambers 53 and 54.

Fluid flows into the chamber 53 through a passage 62, a restriction 63 and an inlet 64. Fluid exhausts from chamber 53 through a fluid outlet passage 65. Fluid flows into the chamber 54 through a passage 66, a restriction 67, and an inlet 68. Fluid exhausts from a chamber 54 through a fluid outlet passage 69. Fluid outlet passages 65 and 69 may be connected to a utilization device such as fluid amplifier 33 shown in FIGURE 1.

OPERATION In operation of the sensor shown in FIGURE 1, power source 20 supplies fluid to chamber 18 through passage 22, restriction 23, and inlet 21. Similiarly, power source 20 supplies fluid to chamber 19 through a passage 25, restriction 2'6, and inlet 24. The fluid flow rates into chambers 18 and 19 are kept relatively constant by holding the supply pressure constant and by providing restrictions 23 and 26 at the inlets to chambers 18 and 19.

Fluid exhausts through the fluid outlet passage 30, the fluid outlet passage 31, and the fluid exhaust aperture 12. The fluid exhaust aperture 12 is very narrow, creating a higher flow resistance through the aperture 12 than through the fluid outlet passage 30 or the fluid outlet passage 31. Consequently, less fluid exhausts through the aperture 12 than through the fluid outlet passages 32 or 31. Fluid that does not exhaust through the aperture 12 must exhaust through the fluid outlet passage 30 and the fluid outlet passage 31. That is, the fluid in the chamber 18 exhausts through the portion of aperture 12 located to the left of piston 13 and through the fluid outlet passage 30. Similarly, the fluid supplied to the chamber 19 exhausts through the portion of aperture 12 located to the right of piston 13 and through the fluid outlet pasage 31.

Let us assume piston 13 is centrally located in housing 11, thus providing that the signals at pasages 30 and 31 3 are equal. Displacing piston 13 to the left shortens chamber 18 and lengthens the chamber 19. Shortening the chamber 18 decreases the length of aperture 12 to the left of piston 13. Hence, the amount of fluid that exhausts through the aperture 12 on the left side of piston 13 decreases. Since the fluid flow to chamber 18 is kept relatively constant, the pressure in chamber 18 rises, and more fluid flows into fluid outlet passage 30, creating a higher pressure in control port 35. On the other side of piston 13, the greater length of the fluid exhaust aperture 12 along chamber 19 allows more fluid to exhaust through fluid exhaust aperture 12. Since the fluid flow to chamber 19 is also kept relatively constant, the pressure in chamber 19 decreases, and less fluid flows into the fluid outlet passage 31. Thus, displacing the piston to the left increases the pressure in the chamber 18 and decreases the pressure in chamber 19. Displacing the piston 13 to the right increases the pressure in the chamber 19 and decreases the pressure in chamber 18. Accordingly, movement of rod 16 varies the differential fluidic signal produced between outlet passages 30 and 31. It is pointed out that pressure between chambers 18 and 19 is not great enough to overcome the friction between piston 13 and housing 11.

The operation of the position transducer 50, shown in FIGURE 2, is similar to the operation of the position transducer 10, shown in FIGURE 1. That is, displacing the rod 60 produces a differential fluidic output signal between fluid outlet passage 65 and fluid outlet passage 69. Position transducer 50 has chambers 53 and 54 of constant volume while position transducer has two chambers 18 and 19 of variable volume. Slowly displacing the piston 13 in position transducer 10, provides a differential fluidic output signal indicative of substantially only the position of piston 13. However, quickly displacing piston 13 results in a pumping action as the air in chambers 18 and 19 compresses and expands because of the volume changes. To eliminate this pumping action and the resulting error in the differential fluidic output signal, chambers 53 and 54 are designed so that their volume remains constant. That is, since pistons 55, 56, and 57 are afiixed to the rod 60 displacement of the rod 60 does not change the volume of the chambers 53 and 54. It has been found that this design produces an accurate differential fluidic output signal with rapidly varying displacement signals.

In FIGURE 2, displacing rod 60 to the left decreases the portion of fluid exhaust aperture 52 to the left of the piston 56 and increases the portion of the aperture 52 to the right of the piston 56. Consequently, with the shorter portion of exhaust aperture 52 on the left of piston 56, less fluid exhausts therethrough, creating a higher pressure in the fluid outlet passage 65. Conversely, with the longer portion of exhaust aperture 52'on the right of the piston 56, more fluid exhausts therethrough, decreasing the pressure in the fluid outlet passage 69.

I claim: 1. A position transducer comprising: housing means having a first chamber, a second chamber, and an elongated exhaust aperture in communication with said first and said second chambers;

moveable means including a piston located between said first chamber and said second chamber, and displaceable along said aperture to vary portions of said aperture accessable to said first chamber and said second chamber;

means for supplying a fluid to said first chamber and said second chamber at substantially constant rates so that variable pressures dependent on the displacement of said piston along said aperture are produced in said first and said second chambers;

means for displacing said piston along said aperture;

and

means for receiving the pressures in said first and said second chambers.

2. The apparatus of claim 1 wherein fluidic amplifier means is connected to receive the pressures in said first and said second chambers.

3. The apparatus of claim 1 wherein said moveable means includes first, second and third pistons, and wherein said first chamber is located between said first and said second pistons and said second chamber is located between said second and said third pistons.

4. The apparatus of claim 3 wherein said first, second and third pistons are separated by fixed distances.

5. Apparatus of the class described comprising:

housing means enclosing a cylindrical cavity, said housing means further defining an elongated fluid exhaust aperture in communication with the cavity along a substantial portion of a length thereof, and fluid inlet means and fluid outlet means each in communication with the cavity; and

piston means located within the cavity and slideable along at least a portion of the length thereof, said housing means and said piston means defining at least one cylindrical chamber in communication with the fluid inlet means, the fluid outlet means and a variable portion of the fluid exhaust aperture, the portion of the exhaust aperture in communication with the chamber being dependent on the position of the said piston means within said housing means.

6. The apparatus of claim 5 wherein:

said piston means comprises a piston which separates at least a portion of the cavity in said housing into first and second chambers each communicating with a variable portion of the fluid exhaust aperture;

the fluid inlet means comprises first and second inlet ports communicating respectively with the first and second chambers; and

the fluid outlet means comprises first and second outlet ports communicating respectively with the first and second chambers.

7. The apparatus of claim 5 wherein:

said piston means comprises a series of first, second and third pistons in a mutually spaced relationship defining first and second chambers within said housing between the first and second pistons and the second and third pistons respectively;

the fluid inlet means comprises first and second inlet ports communicating respectively with the first and second chambers; and

the fluid outlet means comprises first and second outlet ports communicating respectively with the first and second chambers.

8. The apparatus of claim 6 further including:

fluid supply means for supplying fluid to the first and second chambers at substantially constant flow rates, whereby a pressure differential signal dependent on the position of said piston means within said housing is produced between the first and second outlet ports; and

fluid amplifier means connected to the first and second fluid outlet ports to receive the fluid pressure differential signal therefrom.

References Cited UNITED STATES PATENTS 2,784,728 3/1957 Bathurst et al 25l2()5 X 3,220,428 11/1965 Wilkerson 137-815 3,384,338 5/1968 Dermody 251205 M. CARY NELSON, Primary Examiner W. R. CLINE, Assistant Examiner US. Cl. X.R. 

